Refrigerating apparatus



v March '23, 1937'.A H' B, HULL 2,074,911

' REFRIG-ERATING APPARATUS Filed MayzO, 1930 22 5-7\ y HHHHHHHL 40 I 2,; 3 M INVENTOR atented ar. 23, w3?

REFRIGERATHNG APPA'EUS .f Harry B. Hull, Dayton,

Ohio, assignor, by mesne assignments, to General Motors Corporation, a corporation of Delaware Application May 30, 1930, Serial No. 457,580

d Claims.

This invention relates to refrigerating apparatus of the compression type, and more particularly to motor-compressor units for use with refrigerating apparatus of this type.

Refrigerating apparatus of the compression type generally includes among other elements, a compressor having its discharge side connected to a condenser, and its suction side connected to an evaporator, the evaporator being in turn 10 connected to the discharge of the condenser through some sort of a pressure reducing device. Refrigeration is produced by evaporating liquid refrigerant under reduced pressure in the evaporator, the vapors being compressed into and con- 15 densed in a condenser, at a considerably higher pressure. In order tomaintain the evaporator,

or the refrigerator, which generally encloses or houses the evaporator, at a substantially even or constant temperature, it is customary to operate zo the compressor intermittently. That is to say,

it is customary to start the compressor at a certain predetermined high temperature limit, and to stop the compressor at a predetermined low temperature limit.

Since the discharge side of the compressor is under condenser pressure, and since the inlet side of the compressor is under a considerable lower evaporator pressure, it is obvious that the compresser must start under a heavy load unless some 30 means is provided for eliminating the load until the compressor has been brought up to a predetermined high speed by its driving means.

It is to such means that my invention relates, having for one of its objects improved means for 35 automatically loading and unloading the compressor, whereby when the compressor has been brought up to speed by its driving means, it will be automatically loaded, and whereby, when the compressor stops, it is automatically unloaded.

4o More specifically, it is an object of this invention to provide such a loading and unloading means controllable by thermal means.

A further object of this invention is to provide means for maintaining a compressor in an una5 loaded condition until it shall have been brought to a predetermined high speed by its driving member by providing a by-pass leading from the pressure side to the suction side thereof, and by providing a valve, thermally actuated, to control 5o the by-pass passage.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the d5 present invention is clearly shown.

(Cl. E30-22) In the drawing:

Fig. l is a diagrammatical showing of a refrigerating system with the lcompressor shown partly in section and partly in elevation; and

Fig. 2 is a detail view in section of a modified form of actuating means.

In order to illustrate my invention, I have shown diagrammatically, a refrigerating system of the compression type, having `connected therein a compressor embodying features of this invention. For example in Fig. l, I have shown a compressor 20, connected to a condenser 2l through a conduit 22, a liquid receiver 23 connected to the discharge side of the condenser 2l, and an evaporator 24. The refrigerant may flow in a closed path through these parts in the order named. That is to say, the refrigerant is compressed in the compressor 20, forced through the conduit 22 into the condenser 2l, where it is liqueled and nally collected in liquid form in the liquid receiver 23, the liquid refrigerant passing through the conduit 25 into the evaporator 2li which, it should be understood, is located within the cabinet, or within the compartment to be cooled. The refrigerant, evaporating within the evaporator 2t, passes in vapor form through the conduit 25 to the suction side or crankcase of the compressor 20, which will be described in more detail hereinafter. The evaporator may be of any suitable type, and may be, for instance, of the oat controlled valve type disclosed in the patent to Osborne, 1,556,708, patented October 13, 1925. The compressor 20 is shown as driven by an electric motor 2l, and the starting and stopping of the electric motor 2l may be made responsive to the temperature conditions within the evaporator 2d. To this end, a pressure responsive snap switch 28 is operated by a bellows 20' which bellows is connected to the suction pipe 26, the switch being located with the electric motor circuit 29 to thereby start and stop the motor .in accordance with the refrigerant pressure conditions within the evaporator 20. The pressure conditions within the evaporator 2d vary in proportion to the temperature conditions within the evaporator, and consequently the-switch 28 is responsive to the temperature conditions within the evaporator.

The compressor 20 is shown as consisting of a casting. d0 secured to the base plate di by means of the screws i2 and forming therewith a crankcase t3. Above the crankcase the casting LLl0 is formed into a cylinder it, having therein a reciprocating piston l5 provided with a valve ta, and connected to the connecting rod il by the reciprocations of the piston,

' wardly from passage Ato close the valve 63 when wrist pin, (not shown). It should be understood that within the crankcase, opposite aligned bearings 38 are formed'in the walls of the casting 40, within which bearings is mounted to rotate, a drive shaft 46 driven by the motor 21 and connected to the lower end of the connecting rod by means of an eccentric. The upper end of the casting 40 is cut-away interiorly to form a seat for the valve plate 5|, having therein a passage 52 controlled by the outlet valve 53. Above the casting 48, and secured thereto by bolts, one of which is shown at 54, is a cylinder head 55, which cylinder` head forms a pressure chamber 56, having an opening 51 connected to the conduit 22 leading to the condenser.

In order to provide means for loading and unloading the compressor sothat the compressor may operate without load during the first few I provide means in the form of a by-pass between the upper end of the cylinder 44 and the crankcase. To this end, the casting 40 is provided with a passage 66 communicating at its lower end with the low pressure crankcase, and at its upper end communicating with the upper end of the cylinder 44 through a passage 6l. A valve 63, located in the passage 6| is adapted to control communication of passage 6I with passage 60 for a purpose hereinafter more fully set forth. This valve 63 is provided with an operating rod 64, secured at its outer end to the movable plate 66 of the sealing bellows 68, the bellows 68 having its other end secured to the wall of the casting 40. Thus, leakage of refrigerant or other fluid to be pumped, out- 6I along the rod 64 through the packing plug 65 to atmosphere is prevented.

Means are provided for operating the valve 63 the compressor is driven at a predetermined high speed by the motor 21 and to open the valve 63 when the motor stops. To this end, I provide a volatile liquid circuit comprising a container 10, made of some electrical insulating material, which container is connected at its top to a conduit 1I, which conduit is connected at its other end to the interior of a second bellows 12. The bellows 12 has its movable plate 13 secured to a spring 15, the other end of the spring 15 being secured to the movable plate 66 of the bellows 68. Surrounding the container is a resistance or heating coil 11 which coil is connected into the motor circuit by the leads 18, so that it will be in circuit when the motor 21 is in circuit, and out of circuit when the motor 21 is out of circuit. A heat insulating jacket 80 surrounds the coll 11 and the container 10. A bracket 8| having one end connected to the stationary wall 82 of the bellows 12 and its other end connected to the casting 40, supports the entire actuating mechansm in place.

The volatile liquid circuit including the container 16, conduit 1I and bellows 12, contains a volatile liquid, which liquid is adapted, on heatins', to expand, and to contract on cooling, to thereby move the valve 63 inwardly or outwardly as set forth hereinafter.

The device above described operates as follows: When the temperature in the compartment to be cooled is below that required to throw the switch 28 to the on position, the heating or resistance coil 11 will be out of `circuit allowing the volatile liquid within the container 18 to contract or condense, whereby the valve 63 will open, thereby equalizing the pressure on both sides of the piston. When the temperature increases to the predetermined high limit, switch 28 will be thrown to the on position, cutting both the motor 21 and the resistance coil 11 in circuit. The motor 21 will start to drive the compressor and at the same time the resistance coil 11 will be gradually heated to heat the volatile liquid within the container 18. During the first few reciprocations of the piston 45, however, the volatile liquid within the container 10 will not have expanded sufficiently to close the valve 63, and consequently compressed fluid will not pass outwardly through the discharge valve 53 but will pass outwardly through the conduit 6I and back to the low pressure crank case through the conduit 60. After a short interval of time, however, the volatile liquid within the container 10 will have expanded suiliciently to expand the bellows 12, thereby moving the movable plate 13 to the right, causing the spring to move the movable plate 66 of the bellows closing the valve 63. Further'expansion of the volatile liquid will act only against the tension of the spring 15 thereby preventing rupture of the bellows 68 and of the point of valve 65. The closing of the valve 63 is timed to take place after a predetermined interval of time, preferably after the compressor has been brought up to speed by its driving motor 21. This may be accomplished by properly adjusting the amount of volatile liquid within the container 10 or by adjusting the tension of and the flexibility of the bellows 12. q

Thus I have disclosed a compressor having an `.unloading valve operated by thermal means in such a manner that a suillcient time interval is allowed the compressor to come up to full speed before the unloading valve is closed.

In the use of the device disclosed in Fig. 1, the resistance or heating coil 11 is always in circuit when the motor is operating. In view of the fact that the motor operates only a few hours out of about twenty-four, this continuous heating of the coil 11 is of very little importance. However, if desired, the actuating means for the valve may be so constructed that the resistance coil will not be continually in circuit. For example, as shown in Fig. 2, the coil 11 corresponding to the coil 11 of Fig. 1, has incorporated therein a bi-metallic switch 86, which switch is adapted to break the heating circuit at a predetermined high temperature and to make the heating circuit at a predetermined low temperature. It should be understood, however, that the low cut-in temperature of the bi-metallic switch 86 should be above the temperature required to close the valve 63.

The operation of the device shown in Fig. 2 is exactly the same as that shown in Fig. 1 with the exception of the fact that in Fig. 2, the resistance or heating coil 11' is intermittently cut out of the motor circuit during the operation of the motor circuit.

Thus I have disclosed an unloading and a loading device for a compressor operated by thermal means dependent on the motor circuit for successful operation. The lag or time necessary for heating the fluid within the container 10 is sufv ncient to allow the motor to drive the compressor at substantially its normal rate. Further, it should be noted that the valve 63 will not open immediately upon stopping of the motor but will be del. ,'ed until the fluid within the volatile liquid circuit has condensed and thereby contracted.

While the form of embodiment of the invention as herein disclosed constitutes a preferred 68 to the right, thereby form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l. In a compressing unit, a. compressor, a motor for operating the compressor, a switch for starting and stopping said motor, means for maintaining said compressor in an unloaded condition until after the starting period of said motor, said means including a valve, and thermal means for actuating said valve after the starting period of said motor, said thermal means including an electric heating element controlled by said switch.

2. In a compressing unit, a compressor, a motor for operating the compressor, a switch for starting and stopping said motor, means for maintaining said compressor in an unloaded condition until after the starting period of said motor, -said means including a valve, and electrically thermally responsive means controlling said valve, said electrically thermally responsive means being controlled by said switch.

3. In a compressing unit. a compressor, a motor for operating the compressor, a switch for starting and stopping said motor, means for maintaining said compressor in an unloaded condition until after the starting period of said motor, said means including a conduit connecting the high pressure and low pressure sides of said compressor and a valve controlling the conduit, and thermal means for actuating said valve after the starting period of said motor, said thermal means including an electric heating element controlled by said switch.

4. In a compressing unit, a compressor, a motor for operating the compressor, a switch for starting and stopping said motor, means for maintaining said compressor in an unloaded condition until after the starting period of said motor, said means including a conduit connecting the high pressure and low pressure sides of said compressor and a valve controlling the conduit, and thermal means for actuating said valve after the starting lperiod of said motor, said thermal means including an electric heating coil in series with said switch.

HARRY B. HULL. 

